Circuit for detecting current variations
AssigneeInternational Business Machines Corporation
InventorsYves A. Bonnet, Christian Jacquart
Life of this patent
Estimating the term…
Abstract
The circuit of the present invention detects variations of a current I.sub.L flowing in a telephone line LL. A low-value resistor r is connected in series with line LL. A constant voltage generator is connected across this resistor. The current Is applied to resistor r by the contant voltage generator varies as a function of I.sub.L. This being so, a measurement of the variations of Is will reflect variations of I.sub.L and, therefore, can be used to detect both amplitude and directional variations of I.sub.L.
Claims4
A circuit for detecting current variations in a telephone line circuit produced when the telephone set connected to the line circuit goes off-hook comprising:
- a first resitive load, connected in series with the telephone set, in the line circuit;
- a high frequency (HF) generator for generating an HF wave signal;
- a transformer having a centertapped primary winding connected to said HF generator and a secondary winding;
- a rectifier connected to said secondary winding of said transformer;
- a filter circuit connected to said rectifier and said first resistive load;
- means for connecting the centertap of said primary winding to a source of reference voltage through a resistive load;
- and
- means connected to said second resistive load for detecting any voltage variations across said second resistive load corresponding to any said varitions of current flowing through said telephone line circuit and said first resistive load connected therein.
Dependencies are inferred from the claim text.